Integrated Science II
Ch. 6 Explain
Clocks in Rocks
Name __________________________
Period _______ Date _____________
/10
.
Practice Problems:
1. How many half-lives have occurred if the original mass of the parent element was 32g and the mass
afterwards is 1g?
____________________________________________________________________________________
2. What was the original mass of the parent element before radioactive decay if two half-lives have
occurred and the mass of the parent element after radioactive decay was 8g?
____________________________________________________________________________________
3. Find the original mass of the parent element after radioactive decay if three half-lives have occurred and
the mass after radioactive decay is 9.4 kg.
____________________________________________________________________________________
4. If the mass was 20g before nuclear decay and eight half-lives occurred, what was the mass
after?
____________________________________________________________________________________
5. What was the mass before decay started if twelve half-lives occurred and the mass after was
1g?
____________________________________________________________________________________
6. When the mass before and after were 0.8kg and 0.05 kg, respectively, how many half-lives
occurred?
____________________________________________________________________________________
7. What number of half-lives occurred when the mass before decay was 8g and the mass after was
2g?
____________________________________________________________________________________
8. How much mass was left after three half-lives if mass before decay is 1024g?
____________________________________________________________________________________
9. If the mass before decay is 36kg and the mass after decay is 9kg, how many times did the mass
decay in half?
____________________________________________________________________________________
10. If mass after is unknown, what will its value be when two half-lives occur, and the mass before
the decay was 24g?
____________________________________________________________________________________
KEY: Practice Problems:
1. How many half-lives have occurred if the original mass of the parent element was 32g and the mass
afterwards is 1g?
______________5 half-lives_____________________________________________________________
2. What was the original mass of the parent element before radioactive decay if two half-lives have
occurred and the mass of the parent element after radioactive decay was 8g?
______________32 g___________________________________________________________________
3. Find the original mass of the parent element after radioactive decay if three half-lives have occurred and
the mass after radioactive decay is 9.4 kg.
______________1.175 g________________________________________________________________
4. If the mass was 20g before nuclear decay and eight half-lives occurred, what was the mass
after?
______________.08 g__________________________________________________________________
5. What was the mass before decay started if twelve half-lives occurred and the mass after was
1g?
______________4096 g________________________________________________________________
6. When the mass before and after were 0.8kg and 0.05 kg, respectively, how many half-lives
occurred?
______________4 half-lives_____________________________________________________________
7. What number of half-lives occurred when the mass before decay was 8g and the mass after was
2g?
______________2 half-lives ____________________________________________________________
8. How much mass was left after three half-lives if mass before decay is 1024g?
______________128 g__________________________________________________________________
9. If the mass before decay is 36kg and the mass after decay is 9kg, how many times did the mass
decay in half?
______________2 half-lives ____________________________________________________________
10. If mass after is unknown, what will its value be when two half-lives occur, and the mass before
the decay was 24g?
______________6 g____________________________________________________________________
http://library.thinkquest.org/17658/learn/radioprob.html